This invention relates to a machine for testing the sealing capabilities of rotary seals, e.g., seals provided to seal between a rotating shaft and a surrounding non-rotating wall, sleeve, housing, etc.
Rotary seals as contemplated herein are used when a rotating shaft extends through a non-rotating member, e.g., the wall of a housing into which the shaft is extended and wherein a clean environment is to be maintained as compared to a dirty environment outside the housing. An example is the drive line of a four-wheel drive vehicle. The drive line extends from an engine, into and through a transmission and transfer case, to and through front and rear differentials and to the front and rear wheels, i.e. via the front and rear axles. At each of these junctures, drive and driven shafts are interconnected to other drive and driven shafts with various forms of mechanical devices that change drive direction, change gears, connect and disconnect the drive and driven shafts, etc. In each case there is a housing that surrounds the mechanism, bearings that support the mechanism, and one or more rotating shafts projecting into and out of the housing. The drive line is located under the vehicle body and adjacent a roadway where all manner of contaminants (dust, water, mud, snow, exhaust, etc.) make up the outside environment. Leakage of these contaminants into the housing will have a deleterious affect on the mechanical devices and bearings within the housing.
Furthermore the drive line of a four-wheel-drive vehicle is subjected to the hardships inherent when driving the vehicle off-road. The wheel ends of the front and rear axles in particular are subjected to jarring and twisting as the wheels encounter typical off-road surface anomalies such as ruts, rocks, and stream beds. Also, the environment at the wheel ends is the dirtiest as the wheels kick up whatever is present in the off-road environment. A shift mechanism contained in the wheel end whereat, e.g., the front wheels are shifted between two-wheel and four-wheel drive, need to be protected from the outside environment. This is the task of the rotary seal surrounding the drive axle which is projected through a housing and into the shift mechanism at the wheel end. Whereas the invention is applicable not only to other positions in the drive line but to other rotating shaft applications as well, the embodiments here disclosed are directed to the conditions found at the wheel end of a four-wheel-drive vehicle, by way of example only.
Schematically illustrated in FIG. 1 of the drawings is a seal test apparatus of the prior art which is supported on a machine base 11. A shaft 10 is shown mounted to a motor 12. The shaft 10 extends into a canister 16 also supported by the machine base 11. The interior of the canister 16 contains contaminant which represents the outside or dirty environment to which the axle of a vehicle is exposed. (A paddle 18 agitates the contaminant in the canister to insure exposure of the contaminant to the seal being tested.) A seal housing adapter 20 and a shaft adapter 14 are constructed for the test apparatus to duplicate the configuration of the opening 22 through which the shaft 10 will be directed in real life. A seal specimen 24 designed for the opening 22 is fitted to the adapter 20 and the seal 24 is ready to be tested. A fill opening 26 is provided in the canister to input a variety of contaminants and as each contaminant test is completed, the contaminant is drained through drain opening 28 and the canister is refilled with a different contaminant sample.
As illustrated, the test results are determined by viewing or testing leakage through the seal specimen 24 at the inner side of the canister, i.e., between the canister and the motor. Such viewing is severely restricted and unsatisfactory. Also, the test program itself does not adequately represent the stresses to which the seals are subjected in real life.
In the present invention, the test shaft is projected into the canister at the inner wall and continues to be projected through an outer wall formed in part by a housing adapter. A shaft adapter and seal specimen are mounted in the housing adapter. Placement of the seal in the outer wall allows the seal to be directly examined during testing, i.e., they can be viewed straight on from the outer side of the canister. At the inner side, a computer controlled actuator or actuators are mounted to the test shaft. The computer is programmed with information obtained, e.g., at a vehicle test site where sensors installed on a vehicle gather and record the accelerations, displacements, and rpm imposed onto a vehicle axle as the vehicle is driven over a prescribed test route designed to accelerate vehicle wear. The contaminants are circulated through the canister rather than batch filled to the canister. The test results are more easily obtained and the test program itself more accurately represents the wheel end of a vehicle being driven in actual accelerated test conditions.
The invention will be more clearly understood upon reference to the following detailed description and accompanying drawings.